What is season 18 amazing race?

As an AI language model, the last information available for me is about Season 31. However, I can tell you that Season 18 of The Amazing Race premiered on February 20, 2011, and was titled The Amazing Race: Unfinished Business. The season featured eleven teams of returning contestants from previous seasons, including fan favorites and those who had come close to winning in the past. The race covered over 40,000 miles across four continents and ten countries, including Australia, Japan, and China. Ultimately, engaged couple and former Survivor contestants Ethan Zohn and Jenna Morasca came out on top, winning the one million dollar prize.